The present invention relates to rear speaker units which are located at laterally opposite sides of a rear part of a passenger compartment which is defined in a motor vehicle and, more particularly, to rear speaker units for use with a motor vehicle each having a speaker box.
Rear speakers of a motor vehicle are often directly mounted on a rear shelf, linings of side panels or similar structural elements of the vehicle body. Mounting speakers directly on such panels is disadvantageous from the acoustics standpoint, i. e., the panels themselves are caused to oscillate to produce noise and, moreover, the speakers are necessarily oriented upward or in the lateral direction of the vehicle body at the sacrifice of acoustic effects.
To enhance acoustics, a speaker unit having a speaker box at the rear of a speaker has been proposed for use with a motor vehicle. Generally, this kind of speaker unit is disposed on the upper surface of a rear shelf. It is preferable that such a speaker unit be provided with a speaker box having a large capacity in order to enhance the acoustic characteristics, particularly low frequency characteristic. However, since the speaker unit is mounted on a rear shelf as stated above, a large speaker box would not only obstruct the rear view of the vehicle but also show itself to the outside of the passenger compartment to impair the appearance. It is therefore necessary to limit the capacity of the speaker box at the cost of acoustics.
Dead spaces are usually available in the passenger compartment of a motor vehicle such as those spaces which are defined between opposite side panels of the vehicle body and laterally opposite sides of a rear seat. Accommodating speaker boxes in such dead spaces would increase the effective space available in the passenger compartment while insuring attractive external appearance of the vehicle. However, since dead spaces of the kind described are generally elongate in the longitudinal direction of the vehicle body, ordinary speaker boxes cannot be increased in capacity beyond a certain limit. In addition, when ordinary speaker boxes are received in such dead spaces, speakers associated therewith face the front end of the vehicle body due to the fact that the dead spaces are defined at the laterally opposite sides of the passenger compartment. This disturbs the balance of sounds which are emitted from the opposite rear speakers toward vehicle occupants and thereby degrades the acoustic effects.